// https://youtu.be/4HsVCLakjtQ

​

// module aliases

const Engine = Matter.Engine;

// const Render = Matter.Render;

const World = Matter.World;

const Bodies = Matter.Bodies;

​

let engine;

let world;

let circles = [];

let boundaries = [];

​

let ground;

​

function setup() {

  createCanvas(400, 400);

  engine = Engine.create();

  world = engine.world;

​

  boundaries.push(new Boundary(150, 200, width * 0.6, 20, 0.3));

  boundaries.push(new Boundary(250, 300, width * 0.6, 20, -0.3));

}

​

​

function draw() {

  background(0);

  circles.push(new Circle(200, 50, random(5, 10)));

  Engine.update(engine);

  for (let i = 0; i < circles.length; i++) {

    circles[i].show();

    if (circles[i].isOffScreen()) {

      circles[i].removeFromWorld();

      circles.splice(i, 1);

      i--;

    }

  }

  for (let i = 0; i < boundaries.length; i++) {

    boundaries[i].show();

  }

}